As far as I know, breathing air containing relatively high levels of CO2 may get you a headache.
I also know that CO2 level in the fruit bodies of peppers can reach levels as high as 3% at certain stages in development (Blasiak, 2006). So clearly it is possible in a natural setting to achieve these high level of CO2, at least in a micro-environment like around the locules of pepper seeds developing in its fruit.
So I was wondering, if we would have to breath air containing 3% CO2, would get a headache if we breath it in?